1. Field of the Invention
The present invention relates to a method for preparing a patterned substrate by using nano- or micro-particles and, more particularly, to a method for preparing a substrate for a light emitting diode or solar cell.
2. Description of Related Art
Energy insufficiency of the earth has drawn the attention of the researchers to develop more energy sources or to develop some devices for reducing the energy consumption of various electronic devices. Light emitting diodes (LEDs) are advantageous in having high illuminance, low energy consumption, long lifespan, and compact volume, and therefore can be eco-friendly used in various electronic devices.
Recently, in order to enhance a better illuminant efficiency of the LEDs, surface roughening treatments are applied to the manufacture of LEDs to increase light efficiency. During the formation of an epitaxial layer, the supply of different gases or performing of an additional etching process provided after the formation of the layer may improve the roughness of the surface of the epitaxial layer; the surface roughness can improve the light extraction efficiency. On the other hand, by using dry etching technique, the roughness of a sapphire-based substrate can also be increased, whereas the illuminant efficiency of the LEDs may be increased to about 70%.
Solar energy is an infinite energy source that does not create any additional harmful pollution. However, with its high costs and insufficient photoelectric conversion efficiency, solar cells are still not widely used in the daily life. Hence, it has been especially difficult for the researchers to successfully develop a solar cell with high photoelectric conversion efficiency and low manufacturing cost to increase the economic implementation of the solar cell.
Currently, it has been reported that by the incorporating of an antireflective layer, the light transmittance and the photoelectric conversion efficiency of the solar cell may be increased, whereas the reflectivity of the sunlight decreased when the substrate roughening process was applied to the silicon substrate (to pattern the silicon substrate) by a plasma etching method.
Though many methods such as wet and dry etching methods have been developed for surface-roughening of the LED devices or solar cell devices, they are still unfavorable due to their disadvantages such as high manufacturing cost and low alignment precision. Therefore, it is desirable to provide an improved patterning method to approach the roughening function and enable the processing cost to be lowered, and therefore increase the economic implementation of the solar cell.